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Nature vs Nurture meet at UNR cotton harvest

As global economics continue to pressure cotton, interest in ultra-narrow-row (UNR) production systems continues. The USDA's Agricultural Research Service (ARS) is refining UNR management methods to maintain harvest quality and improve payback. What is emerging is that both nature and nurture play well-defined roles in getting the best from the stripper-harvested cotton.

UNR is typically grown in 7.5- to 10-inch rows in densities of about 120,000 seeds per acre vs. 40,000 seeds per acre in conventional (38- to 40-inch) row cotton. A stripper is required for harvesting because the spindles on a traditional harvester cannot be set close enough for the narrow rows.

William T. Molin, plant physiologist, with the ARS's Southern Weed Science Research Unit in Stoneville, Miss., says that UNR quality begins with variety selection and continues through harvest preparation. “If the crop is properly prepared and gins take extra precautions, we can get cotton that's nearly equal in fiber characteristics to wide-row cotton,” says Molin, who is conducting a multi-year study to refine UNR cultural practices.

Trash and barkiness tend to be a problem with UNR cotton that has not been properly prepared, he says. As in conventional row cotton, the initial harvest preparation for UNR cotton includes a defoliant. Molin likes what he sees with Ginstar — among several alternatives, but further research is needed.

“Then as an added step, the top 6 to 9 inches of the plant must be killed with a burndown treatment, such as with a paraquat product,” he says.

Syngenta, the new agribusiness company formed by the merger of Novartis Agribusiness and Zeneca Agrochemicals, replaced Starfire with Gramoxone Max for the 2001 growing season. Sold as Cyclone Max in Texas, New Mexico and Oklahoma, Gramoxone Max is a more-concentrated formulation of Starfire that allows growers to treat the same number of acres with fewer containers.

Efficient weed management and thorough desiccation prior to harvest also reduce the amount of plant contamination or “trash” that goes into the module, Molin says. The stripper picks up more trash than conventional pickers, although on-board cleaning systems help reduce trash.

Three years into the multi-year study, Molin says that the yield between stripper and conventional cotton is essentially the same. Mid-season cultivation and lay-by herbicide applications are eliminated with UNR. In terms of production costs, seed costs are higher for UNR, but a shorter growing season due to an earlier-terminated crop and fewer mid-season operations can reduce crop inputs.

Equipment needs are also simpler. A stripper costs about half as much as a spindle picker, and it can move faster, he says. “When the maximum economic return is considered, as opposed to maximum yield, there may be a savings with UNR that allows a grower to produce a cheaper crop.”

Reducing bark and gin trash begins with variety selection. After numerous side-by-side variety tests, Molin says some varieties are not only higher yielding, but tend to clean up better coming out of the field. “The trash that's taken into the stripper is cleaned more efficiently. Whether the branches are more fragile, produce less entanglements, or what, the trash just separates better.”

The ARS is also testing new varieties, including genetically modified ones, to identify those best-suited for the way UNR is grown and harvested. Generally, that means higher yield.

But nature has its limits, and nurture is also important to achieving plants ideally shaped for stripper harvesting. Weed management is important. Growth regulators keep plants in check and dense stands control the length of fruiting branches. Longer branches can generate more bark and trash, which is an issue in stripper harvesting.

In the same vein, letting Mother Nature do the work of dry-down contributes to barkiness. Research leader Stanley Anthony at the ARS's Cotton Ginning Laboratory in Stoneville says the number of “bark” calls from the classing office have decreased dramatically in recent years as Texas farmers have moved from allowing frost to defoliate stripper cotton to using controlled chemical termination.

Anthony believes plants that are quickly terminated while growing seem less likely to shed bark during stripper harvesting. “When Mother Nature terminates the plant, then the adherence of the bark to the plant deteriorates pretty quickly,” he observes. “So if you can defoliate and harvest in a timely manner, I think that's going to reduce the bark more than anything.”

When cotton is properly defoliated and desiccated, leaves and stems are not a problem, but limbs and stalks — which create bark — are, he says. Bark is difficult to remove at the gin.

“Generally, we can produce stripper-harvested cotton that's as clean as cotton that was harvested with a spindle picker by using an additional stage of stick machine and an additional saw-type lint cleaner. Unfortunately, we currently find more bark, more short fiber and more neps in stripper cotton,” Anthony says.

“Having the right variety to begin with and close management by the farmer will help us back off some of the additional cleaning that's currently required at the gin with UNR,” he says.

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